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Re: RFC2821bis-01 Issue 8 number of message transactions per connection ?

2007-03-29 08:40:35

On 3/29/07, Tony Hansen <tony(_at_)att(_dot_)com> wrote:

<implementor's hat>

  Side note: An implementation is free to respond with 4xx (e.g., 421,
451 or 452) to the MAIL FROM whenever it wants to shut down the
connection. And some implementations *do* choose to do so because of
local policy decisions.

</implementor's hat>

Recently I've encountered servers that respond with 221 rather than
250 at the end of the DATA phase (after <CRLF>.<CRLF>) and then
immediately close the connection.  (This may not be a
recently-developed practice, but I noticed it for the first time last
week in an SMTP client log when tracking down a delivery problem.)

It would appear this is meant as an indication that the server intends
to accept exactly one message and doesn't care to wait for a QUIT.

I'm not sure what, if anything, could be put into the document about
this.  Perhaps guidance as to how clients should react when the server
wanders off-protocol?  In the case I was investigating the client
treated the situation as a 4yz and retried the message later, leading
to a lot of copies being delivered and (fortunately just one) irate

(I've also seen 221-and-close responses to EHLO, which seems entirely bizarre.)

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